BARRY Bloomer headed the Welders into a 31st minute lead when he met an Andrew Dickson cross from the right following a short corner.
Craig McMillen added to the home advantage on 50 minutes from the spot after Arron Lemon had upended Ryan Brown in the area.
Larne pulled a goal back on 74 minutes after Paul Maguire made the most of a long Brendan Quinn clearance which caused a moment of confusion in the home defence.
But any hopes the visitors had of salvaging a point were dashed with three minutes remaining when McMillen stroked home his second penalty of the game after he had been brought down by Jamie Marsh.
HW Welders: Dougherty, McMurray, Armstrong, Harris, Rezai, Cahoon, King, Dickson, McMillen, Bloomer, Brown subs Harvey (replaced Bloomer 66), Marks (replaced King 80), McLoughlin (not used), Muir (not used), Miskelly (not used)
Larne: Quinn, Marsh, Lemon, White, Brown, Yilmaz, McAllister, McClean, Maguire, Dick, Young subs Todd (not used), McNally (not used), Moore (not used), Workman (replaced Dick 65)